Solder alloys not containing Pb are actively being developed. Currently, a Sn—Ag based solder alloy and a Sn—Cu—Ni based solder alloy are the mainstays. Sn—Cu—Ni based solder is advantageously low in material costs in comparison with Sn—Ag based solder. A Ni based solder alloy having a composition disclosed in a patent granted to the applicant of this application is available as a Sn—Cu—Ni based solder alloy and has a Sn-0.7 wt % Cu with 0.05 wt % Ni added thereto.
Metal resources have been more and more difficult to obtain in recent years. The recycling of metals is thus demanded in view of a sharp rise in material costs and earth environment. The above-described Sn—Cu—Ni based solder alloy has a Sn concentration of about 99 wt %, and it is important to recycle Sn.    Prior Art: Japanese Patent No. 3152945